20.500.12556/RUL-175008 High-intensity focused pressure wave generation via Q-switched Er:YAG laser with a water layer formed by the coupled lens for optoacoustic conversion We demonstrate coating-free optoacoustic generation and focusing of ultrasound using a mechanically Q-switched (MQS) erbium-doped yttrium aluminum garnet (Er:YAG) source (~100 ns, ≤20 mJ) combined with a concave water interface that simultaneously serves as converter and acoustic lens. Axial, lateral, and focal-point measurements mapped the pressure field while varying beam diameter (2w = 5–15 mm) and pulse energy (E = 10–20 mJ). The maximum focal positive pressure (P▫$_max$▫ = 7 MPa) occurs at an intermediate diameter (~10 mm), whereas the tightest lateral/axial confinement and strongest spectral enhancement arise at larger diameters (14–15 mm) with f▫$_c$▫ = ~5 MHz and −6 dB bandwidth up to 7 MHz. Pressure increases nearly monotonically with energy. For equal fluence, larger diameters yield higher focal pressures due to greater focusing gain. Small beams (2w ≈ 5–7 mm) show shorter apparent time-of-flight (TOF) and waveform broadening, consistent with early shock-like emission from locally vaporizing region. These results provide practical rules for tuning amplitude, spectrum, and confinement, enabling sub-millimeter focusing for contamination-sensitive and therapeutic applications. focused pressure wave photoacoustic Q-switch Er:YAG fokusirani tlačni valovi optoakustika preklop kvalitete Er:YAG true false true Angleški jezik Slovenski jezik Članek v reviji 2025-10-13 12:55:35 2025-10-13 12:55:44 2025-12-03 03:42:47 0000-00-00 00:00:00 2025 0 0 17 str. issue 19, [article no.] 10860 Vol. 15 2025 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 535:534 2076-3417 10.3390/app151910860 252918019 https://www.mdpi.com/2076-3417/15/19/10860 1 ea0f22a9-a822-11f0-9328-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=219933 Fakulteta za strojništvo 0 0 0